The elimination of dust particles or other impurities from the air within industrial plants or other areas where the air becomes contaminated by sawdust, larger wood chips, metal filings, or the like is increasingly important in modern industry. In addition to the economic necessity of minimizing the expense of contaminated air, ecologists are demanding maximum purification of air before it is released back into the atmosphere.
There are several known types of dust eliminators or separators, and the cyclone-type separator is generally considered to be one of the more efficient and less expensive types. In known types of cyclone separators, a contaminated air stream generally enters a cylindrical chamber tangentially through an upper inlet and follows a helical, downwardly inclined path. The heavier dust particles are urged to the outside wall by centrifugal force, whereupon the force of gravity pulls the dust particles down the walls and through a conical lower portion into a receptacle when the velocity of the air stream falls to such an extent that the dust particles are no longer entrained therein. The clean air, after separation turns and exits through a discharge cylinder which extends down from above into the separation chamber.
One problem that occurs in such types of separators is that after the air stream makes one revolution, the dust already separated becomes reentrained in the subsequent air stream which tends to keep it suspended within the separator, rather than falling out the bottom. In such types of separators, the air stream continues in its helical path down into the lower areas of the separator, with the result that some of the air that is discharged through the discharge cylinder and out the top includes dust entrained therein, and some of the dust which escapes through the bottom also includes part of the air stream which is deleterious to the separating process.
Also, where the air stream which initially enters the separator is at a high velocity, the diameter and length of the separator must be relatively large in order that complete separation occurs without reentrainment of the dust into the existing clean air.